This research evaluates the use of a mixture of beetroot and carrot pomace (Pomace-Biochar) to synthesize high surface area activated cathode materials for zinc-ion hybrid supercapacitors (ZIHSCs). The comprehensive analysis of a zinc-ion hybrid supercapacitor (ZIHSC) is based on the chemical modification of Pomace-Biochar using phosphoric acid (H3PO4) and potassium hydroxide (KOH) chemical agents. The Zn//2 M ZnSO4// Pomace-KOH device exhibits a high energy density (263.7 Wh Kg(-1)), due to enhancements in surface defects, pore size, and surface area, which ameliorate the electrochemical performance. Additionally, the Zn//2 M ZnSO4//Pomace-KOH device exhibits outstanding capacity retention (80 % similar to 31,000 GCD cycles), indicating long-term stability.

This study focuses on the synthesis and characterization of zinc cobaltite (ZnCo2O4) as an electrode material for supercapacitor (SC) applications. ZnCo2O4 was synthesized via an efficient sol-gel method, followed by annealing. Morphological and structural character­ri­za­tions revealed that ZnCo2O4 forms as nanoflakes with a well-crystallized structure. Electro­chemical parameters of ZnCo2O4 were examined by various electrochemical techniques in a 3 M KOH aqueous electrolyte. The highest specific capacitance (Csp) of 321 F g-1 was obtained at a current density of 0.8 A g-1. The electrochemical performance of the ZnCo2O4 electrode is superior, owing to its porous nanoflake morphology, which provides numerous active sites and enables substantial charge storage. Moreover, multiple oxidation states of Zn and Co enhance redox reactions at the electrode surface, thereby improving the electrode's pseudocapa­citance. The superior electrochemical performance of ZnCo2O4 indicates that it is a promising cathode material for hybrid SC devices.

This study presents the synthesis of single-phase 2H-MoSe2 and one-pot synthesis of MoSe2/rGO (MSR) composite used for the detection of environmental pollutants (NO2, NH3, H2S CO2, CO, CH4, CH3COCH3) at ambient temperature (similar to 25 degrees C). The gas sensing devices were fabricated on Ti/Pt interdigitated electrodes with different compositions of MSR composite viz. 10 (MSR-10), 20 (MSR-20), and 30 (MSR-30) weight % of rGO. The sensitivity of the p-type MoSe2, rGO and MSR-20 was calculated to be similar to 29 %, similar to 24 % & similar to 38 %, respectively at 4 ppm concentration of NO2. The respective response and recovery time were calculated to be 191/218 s, 225/412 s, and 110/128 s for MoSe2, rGO, and MSR-20 composite at 4 ppm of NO2 gas. The response curve at the lowest detection limit indicates stable performance of the device, which makes it suitable for its real-time application. The response time and recovery time of the composite device are 40 s and 65 s, respectively at 100 ppb concentration of NO2 gas. The sensing device was subjected to 0.1 ppm to 4 ppm of NO2 gas concentration, and the obtained device response was highly repeatable and stable after 60 days. The possible gas sensing mechanism based on charge transfer is proposed for fabricated devices using MSR composite material. The gas sensing device parameters, selectivity, repeatability, sensitivity, and stability show a great potential of MoSe2-rGO composite material in gas sensing.

Aqueous sodium-ion batteries (ASIBs) are promising for energy storage applications because of their low cost and safe operational properties. Mn-based layered transition metal oxides are favorable positive electrode materials for ASIBs. Still, rapid capacity decay due to the Jahn-Teller effect and Mn dissolution in the aqueous electrolytes during cycling restrict their applicability. To resolve these issues, a dual strategy of using a hybrid electrolyte and doping is used to suppress the hydroxide formation during electrochemical cycling to boost the performance of ASIBs. Cu and Fe dual ion doped Na0.7MnO2 (NFCM) is synthesized via the solid-state method for cathode material. The X-ray diffraction spectra confirm good crystallinity and the presence of the P2 phase in pristine and doped samples with minimal impurity. Scanning electron microscopy shows rod-like structures for pristine Na0.7MnO2 (NMO), while the doped sample comprises both rod-like and sphere-like structures. The full cell configuration of doped NFCM || activated carbon results best with a hybrid 1 M NaClO4 electrolyte with a discharge capacity of 141 mAh g⁻¹. The binding of OH⁻ ions with ethanol through hydrogen bonding leads to a decrease in Mn dissolution and a stable cycle life of up to 100 cycles.

This study investigates the utilization of Citrus limetta waste pulp as a renewable agro-waste-derived material for energy storage applications, specifically in zinc-ion hybrid supercapacitors (ZIHSCs). Soft-templated synthesis is employed to synthesize the porous template biochar (CL@CTAB_850°C) through hydrothermal treatment followed by pyrolysis at 850°C. To boost the surface properties of the porous template, it undergoes further chemical treatment (H3PO4), resulting in improved physicochemical and electrochemical performance. The fabricated ZIHSC device exhibits high electrochemical performance for CL@CTAB@H3PO4_850°C cathode. The scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) results confirm the porous nature of the materials. The ZIHSC device exhibits excellent self-discharge behavior with high voltage retention, addressing key challenges in current energy storage technology and advancing its potential for practical implementations. This research highlights a resource-efficient and waste-valorizing approach for creating high-performance carbon electrodes, demonstrating the potential of agro-waste valorization in energy storage and ZIHSC devices.

Herein, we present interdigitated microelectrode nitrogen dioxide (NO2) gas sensor by utilizing layered nanosheets of tungsten diselenide (2H-WSe2) intercalated with reduced graphene oxide (rGO). The 2H-WSe2 nanosheets and its composite with rGO were prepared through simple solvothermal process, resulting in intercalation with rGO sheets. Comprehensive investigation of gas-sensing properties of WSe2-rGO (WSR) composite nanosheets with their high selectivity and sensitivity to NO2 detection at ambient temperature have been performed. The WSR sensor achieved notable responses of similar to 2.9%, similar to 25.9%, and similar to 39% at NO2 concentrations of 50 ppb, 1 ppm, and 4 ppm, respectively. Furthermore, the sensor efficiently maintained good response of similar to 30.8% to NO2 gas even after 210 days of testing, demonstrating its outstanding long-term stability.

Sodium manganese oxide (NaxMnO2) is the preferred cathode for aqueous sodium-ion batteries (ASIBs) in large-scale energy storage systems. However, the structural instability, presence of the Jahn-Teller-active element, manganese dissolution, and surface degradation during cycling lead to capacity fading and unstable interface formation when used as a cathode in ASIBs. Additionally, the lattice changes during charge-discharge results in nanovoid and crack formation. Addressing the issue of the construction of high-capacity cathode materials with superior stability is most important to improving the performance of ASIBs. Here, these significant issues are addressed by incorporating heteroatoms in the structure; a Na0.7Fe0.1Cu0.1Li0.18Ti0.1Mn0.52O2 (NFCM-LT) cathode exhibits an excellent rate capability at 3C with 78% capacity retention after 140 cycles in an ASIB. To investigate the material degradation deeply, precycling and postcycling ex situ Raman spectroscopy for structural changes during charge-discharge, scanning electron microscopy for imaging of structure degradation after 1500 cycles, and X-ray photoelectron spectroscopy (XPS) technique for the ratio of Mn4+/Mn3+ in the material are used. The Mn3+/Mn4+ ratio in the material before and after the cycling through ex situ XPS indicates a reduction in Jahn-Teller distortion, which results in extraordinary cyclic stability until 1500 cycles at 10C. The cathode material delivers a specific capacity of 132 mA h g(-1) in the first cycle at the current rate of 1C.

Design and development of battery-type electrode materials with high capacitance, wide potential window, and desirable cycle stability are essential to enhance the performance of hybrid supercapacitors (HSC). In this study, a simple sol-gel synthesis strategy has been adopted to fabricate spinel NiCo2O4 nanoflakes. The morphological and structural analysis shows that the NiCo2O4 is formed with nanoflakes morphology having high phase purity and good stoichiometry. The electrochemical study of the NiCo2O4 electrode in 1 M Na2SO4 aqueous electrolyte reveals that the electrode has a maximum specific capacitance of 488 F g(-1) at 2 A g(-1). Detailed electrochemical examinations of cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS) profiles reveal the pseudocapacitive charge storage kinetics of NiCo2O4 electrode. Furthermore, a hybrid supercapacitor device is constructed by employing molybdenum-disulfide (MoS2) & reduced graphene oxide (rGO) nanocomposite and NiCo2O4 as the negative and positive electrodes, respectively. PVA-Na2SO4 is utilized as the polymer gel electrolyte. The HSC device delivered the highest specific capacitance of 106 F g(-1) at a current density of 0.8 A g(-1) with superior cyclic stability. Thus, exploring strategies for superior performance through material modification and selection of suitable electrolyte has been useful and makes this study significant among the reported related works.

The recent surge in developing highly porous cathodes (HPC) derived from waste biomass sources for zinc-ion hybrid super-capacitors (ZIHSCs) has sparked significant interest. This study uses an inexpensive precursor technique to explore a cost-effective approach by converting bougainvillea flowers (BG) into biochar (BG-Biochar). Biochar that experienced chemical activation treatment has significantly increased porosity and surface functional group. The phosphoric acid (H3PO4) treated biochar (BG-H3PO4) demonstrates superior performance compared to both potassium hydroxide (KOH) treated biochar (BG-KOH) and untreated BG-Biochar in ZIHSCs. The ZIHSC device, based on BG-H3PO4, achieves the maximum specific capacitance and specific capacity at 0.1 A g− 1 current density. Furthermore, this work contributes to understanding biochar-based cathodes, shedding light on the influence of different activation treatments on porosity and surface characteristics. The findings emphasize the potential of bougainvillea flower-derived biochar as a promising material for energy storage applications, particularly in ZIHSCs. The notable electrochemical performance of BG-H3PO4 highlights the significance of tailored chemical activation in optimizing biochar properties for enhanced super-capacitor applications.

Polycrystalline Mg2Si thin films of varying thickness were grown on (100) Si substrate by employing extensive surface diffusion of elemental atoms. At first, magnesium atoms were deposited on (100) Si substrate with the aid of radio frequency magnetron sputtering; in order to promote interdiffusion of Mg and Si, annealing was carried out in hydrogen atmosphere at the temperature of 500 °C for a period of four hours. Films of thickness values 500 nm and 100 nm were prepared for further study. Electrical transport behaviour of thin films was studied by measuring Hall conductivity, charge carrier concentration and its mobility. Moreover, current-voltage characteristics of Mg2Si thin films were studied by four probe colinear method. Structural analysis was done through X-ray diffraction study; microstructural study was conducted in SEM. While X-ray Photoelectron Spectroscopy (XPS) was used for securing chemical information of the film surface, Energy Dispersive Spectroscopy (EDS) was also employed to know the elemental composition of Mg2Si thin films. Further, Atomoic Force microscopy (AFM) was conducted for topographic study. It was found that the Mg2Si thin films prepared in the present investigation behaved as degenerate semiconductor with the maximum attainable conductivity of in the range of 102 S/m. Further, it was observed that the conductivity of higher thickness Mg2Si thin film( 1000 nm) was lower than that of lower thickness film ( 500 nm ) at all the test temperature.

A facile synthesis route for preparing manganese dioxide (MnO 2 ) with unique nano-needle morphology and its nanocomposite with reduced graphene oxide (MnO 2 –rGO) for high energy density quasi-solid-state asymmetric supercapacitor.

In the realm of advancing energy storage technologies, the efficacy of natural biomass sources in mitigating environmental constraints has gained prominence. This study delves into the evolving landscape of energy storage devices, specifically batteries, super-capacitors, and the nascent domain of zinc-ion hybrid super-capacitors (ZIHSC). The focus centers on biomass-derived highly activated carbon, a burgeoning field of research esteemed for its diversity, environmental compatibility, distinctive structural attributes, and unique surface characteristics. This investigation presents a comparative analysis of activated carbons derived from ground nutshell (GS) in the context of ZIHSC applications. Emphasis is placed on the significance of a straightforward biochar synthesis process and subsequent chemical activation. The activated biochar, denoted as GS-H3PO4 and synthesized using H3PO4, exhibits a discernibly higher Brunauer Emmett Teller (B.E.T.) surface area when juxtaposed with pre-carbonized ground nutshell (GS-Biochar).The ZIHSC cell incorporating GS-H3PO4 manifests noteworthy energy density metrics, registering at 50.28 Wh Kg−1 (100 W Kg−1) and 11 Wh Kg−1 (2 kW Kg−1). Additionally, it demonstrates a specific capacitance of 199 F g−1 (2 mV s−1). These findings underscore the promising potential of H3PO4-derived activated carbon in optimizing cathode performance for Zinc-ion hybrid super-capacitors. This study contributes to the growing understanding of biomass-derived materials, offering insights into the nuanced interplay between synthesis methods and electrochemical properties, crucial for advancing sustainable energy storage solutions.

The race to achieve cost-effective power sources has led to intense research to explore natural sources, and biomass sources are the front-runners. In this work, the chemical activation of the banana peel was carried out using phosphoric acid (H3PO4) to develop a high-performance zinc-ion hybrid super-capacitor (ZIHSC). SEM (Scanning Electron Microscopy) morphology of chemically activated BP-H3PO4 materials revealed a nano-porous structure, and BET (Brunauer-Emmett-Teller) further corroborates the enhancement in surface area (218.339 m2 g- 1) of banana peel biochar. The process yields a low synthesis cost due to the facile conversion of biomass to biochar and activated biochar. The phosphoric acid (H3PO4) treated banana peel for the ZIHSC device showed an excellent specific capacitance of 228 F g- 1 (1 mV s- 1, scan rate), an energy density of 120 Wh Kg- 1, and a specific capacity of 73.98 mAh g- 1 (0.1 A g- 1, current density). The two-electrode Swagelok-based ZIHSC cell retains incredible capacity retention after 50,000 charge and discharge cycles.

From the perspective of the lithium resources situation on earth, it is very vital to develop sodium-ion batteries (SIB) as lithium-ion technologies alternatives. Delivering high capacity along with adequate capacity retaining is difficult in designing favorable cathode material for SIB. Among all of the positive electrode (cathode) materials for SIB, layered transition metal oxides (LTMO) with remarkable properties have attracted intensive interest. In this work, we intend to enhance the electrochemical behavior of O3 Na[Fe0.27Cu0.27Mn0.46]O2 (NFCM) in SIB with graphene oxide in reduced form (rGO), as the negative electrode (anode) material. X-ray diffraction spectrum confirms the presence of expected phase of LTMO. Electrochemical impedance spectroscopy (EIS), Galvano static charge–discharge (GCD), and Cyclic voltammetry (CV) are performed, and material delivers a excellent specific capacity value of 116 mAhg−1 with efficient capacity retention at the current rate of 1C.

In the current study, we report a straightforward and affordable sol-gel preparation approach for the fabrication of spinel CuCo2O4 nanorods for sodium ion-based hybrid supercapacitor. The morphological and structural analysis shows that appropriate purity nanorods of CuCo2O4 are formed with good stoichiometry. The electrochemical study of CuCo2O4 nanorods reveals that the electrode has highest specific capacitance of 367 F g(-1) at 1 A g(-1) in 1 M Na2SO4 electrolyte. Evaluation of the diffusion kinetics of sodium ions through detailed electrochemical evaluations of cyclic voltammogram (CV) showing the charge storage kinetics of CuCo2O4 is primarily performed through the diffusive limited mechanisms, suggesting the battery-like behavior of CuCo2O4 electrode. Hybrid supercapacitor (HSC) device is fabricated by utilizing CuCo2O4 for positive and reduced graphene oxide (rGO) for negative electrodes material. The polymer gel electrolyte is used in the form of hydrogel membrane made of PVA and Na2SO4, and the HSC device (rGO || CuCo2O4) exhibits energy density of 9.18 Wh kg(-1). Therefore, sodium-ion hybrid supercapacitor electrode materials for this investigation are established using a comprehensive electrochemical kinetics.

The design and development of an alternative counter electrode (CE) using graphenebased low-cost material for the dye-sensitized solar cell (DSSC) is the major motivation of the current research to replace the traditional platinum counter electrode. Herein, we prepared reduced graphene oxide (rGO) and investigated it for an efficient CE in DSSC. The structural and morphological properties of rGO are analyzed using FESEM, TEM and Raman techniques. The performance of I3- reduction on the CE is characterized by the EIS Nyquist plot, cyclic voltammetry, and the Tafel curve. The measured electrochemical results suggested that rGO CE has a lower charge transfer resistance (Rct), higher cathodic current density (Jrd), and higher Tafel slope as compared to graphene oxide (GO) CE, revealing that rGO CE has good catalytic activity towards the I3- reduction.

In this study, the toxic gas detection ability of chemical vapor-deposited (CVD) monolayer graphene (MLG) is examined. The electron beam deposition technique is utilized in order to deposit silver (Ag) onto a pliable polyethylene terephthalate (PET) substrate for the production of the interdigitated electrode (IDE) composed of the aforementioned material. The grown CVD graphene is transferred through PMMA-free approach using PVA on the IDE-deposited PET substrates. Raman spectroscopy mapping revealed an appropriate quality of MLG with uniformity. The use of both FE-SEM and HR-TEM allows for a comprehensive analysis of the growth of monolayer graphene. FE-SEM provides information about the surface morphology, while HR-TEM gives details about the structure and atomic arrangement of the material. The gas sensing characteristics of the fabricated sensing device are tested for environmental pollutants (NO2, NH3) at room temperature. The sensing mechanisms in the presence of oxidizing and reducing gases are further discussed. The response/recovery time and sensitivity are also evaluated, and the MLG gas sensor showed good stability and repeatability.

This paper reports the results of a study on the effect of N-ion implantation on structure and properties of Magnesium Silicide (Mg2Si) thin film that is known to be a potential thermoelectric (TE) material. Mg2Si thin films of thickness 300 nm have been deposited on the silicon (100) substrate at room temperature using the sputtering technique. The thin films have been subjected to 50 keV N-ion implantation under various fluence values ranging from 5 × 1014 to 1 × 1016 ions/cm2. Structural characterization by X-ray Diffraction (XRD) technique has verified that the pristine thin film is constituted by a crystalline single phase Mg2Si material; however, ion irradiation leads to partial amorphization of the Mg2Si thin film. Field–Emission Scanning Electron Microscopy (FE-SEM) with Energy Dispersive Spectroscopy (EDS) is employed to obtain microstructural and compositional information. While particle coarsening due to ion implantation is affirmed by FESEM observation, the EDS study cannot authenticate the exact stoichiometry of the film due to substrate effect. X-ray Photoelectron Spectroscopy (XPS) study was conducted to secure information about the chemical state of the elements at the film surface which confirms the presence of Mg2Si phase in the pristine film; and of both Mg2Si and nitrogen in the implanted thin films. The electrical transport behavior of Mg2Si thin films have been studied by way of I-V and Hall measurements; the conductivity values are found to increase from 6*102 S/m to 1.17*103 S/m as the fluence is raised from 5 × 1014 to 1 × 1016 ions/cm2 at a temperature of 150 °C. The electrical conductivities of all the samples are seen to increase continuously with increasing temperature thereby, showing semiconducting behavior of the thin films.

In this study, micro flower-like molybdenum disulfide (MoS2) is directly grown on reduced graphene oxide (rGO) sheets by a new one-pot facile hydrothermal strategy with different MoS2-rGO combinations (such as 1:1, 1:2 and 2:1, respectively). The structural and morphological study demonstrate that MoS2 flowers are uniformly distributed on the rGO sheets. The capacitive performance of synthesized samples has been evaluated by various electrochemical techniques, using a three-electrode set-up in 1 M Na2SO4 electrolyte. The electrochemical results reveal that the MoS2-rGO (1:2) offers the highest capacitance of 352 F g(-1) at a current density of 0.2 A g(-1). Further, the charge storage kinetics of MoS2-rGO (1:2) electrode have been evaluated by in-depth analysis of the Cyclic Voltammetry (CV) profile, implying that the charge storage mechanism contributes to both capacitive and diffusion-controlled processes. Three symmetric supercapacitor (SC) devices are fabricated using three afore-mentioned compositions as the active material with polyvinyl alcohol (PVA)/Na2SO4 hydrogel membrane as the separator-less electrolyte. The symmetric SC device (MoS2-rGO (1:2) || MoS2-rGO (1:2)) based on MoS2-rGO (1:2) as the electrode material demonstrates maximum capacitance value 256 F g(-1) at 0.15 A g(-1). This strategy to combine the appropriate amount of MoS2 with rGO sheets has enhanced the electrochemical performance of MoS2-rGO composite due to the formation of a hetero-interface between MoS2 and rGO composite leading to fast ion propagation and facilitate the development of advanced quasi-solid-state energy storage devices.

The present work reports a quasi-solid state sodium ion-based asymmetric supercapacitor (ASC) device with nitrogen-doped reduced graphene oxide (NrGO) and boron-doped reduced graphene oxide (BrGO) electrodes. The choice of NrGO (BrGO) for the cathode (anode) is accomplished through a computational investigation of electrode quantum capacitances based on density functional theory (DFT). Nanocellulose is used as an electrode binder due to its biodegradability, enhanced wettability, good ion permeability, and low cost. The NaClO4-PVA based hydrogel membrane is the separator-less quasi-solid state gel electrolyte in the fabricated device. The specific capacitance of the NrGO || BrGO ASC device is obtained as 251.2 F g-1, at a current density of 1 A g-1 with a wide potential window of 2.5 V which is better than the previous reports. This device offers a better performance in comparison to the rGO||rGO, NrGO||NrGO and BrGO||BrGO symmetric supercapacitor (SSC) devices due to the synergistic effect of non-faradic capacitance and pseudocapacitance. The ASC device shows an energy density of 54.5 Wh kg-1 at a power density of 1.25 kW kg-1 and significant capacitance retention of 84.8% after 10,000 cycles at a high current density of 15 A g-1.